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Low-cost, Efficient, Flexible Solar Cells with 3D Nanopillar Arrays




Ali Javey and Zhiyong Fan at Berkeley Lab have invented a method for growing highly regular, single-crystalline nanopillar arrays of optically active semiconductors to produce efficient, 3D solar cells. The Berkeley Lab invention uses a “vapor-liquid-solid” process that produces large-scale modules of dense, ordered arrays of nanopillars. The 3D configuration allows for less stringent requirements in terms of the quality and purity of the input materials, providing for a reduction in cost compared to other solar cell configurations.

The inventors tested the method by producing a solar cell composed of electron-rich CdS nanopillars embedded in a polycrystalline thin film of hole-rich CdTe. The efficiency of this prototype was 6%, which may be readily improved with concentrators, more transparent top contacts, and optimization of the nanopillar dimensions. The technology was also used to produce solar modules on flexible substrates that offer more efficient light absorption and carrier collection than rigid arrays. These flexible arrays could be bent repeatedly without damage or loss of cell performance.   3D solar cell of nanopillars. An aluminum substrate (dark grey) forms the bottom electrode and is combined with a highly periodic anodic alumina membrane (light blue) to create a template for an array of cadmium sulfide nanopillars. The next layer up is a cadmium telluride film (green), then a top electrode of copper and gold (yellow), and finally a superstrate (light grey).  

The ability to deposit single-crystalline semiconductors on support substrates is crucial in the development of efficient photovoltaics. However, the process, usually performed with epitaxial crystal growth, has been expensive and inefficient. In addition, when amorphous substrates have been used to grow single-crystalline nanowires non-epitaxially, at less expense, the nanowires have varied in size, alignment, and density giving the resulting arrays a limited efficiency of approximately 0.5%. The Berkeley Lab technology offers a significant improvement in efficiency and manufacturability.

DEVELOPMENT STAGE: Proven principle.

STATUS: Published Patent Application WO2011005462 available at Available for licensing or collaborative research.


Fan Z., H. Razavi, J.-W. Do, A. Moriwaki, O. Ergen, Y.-L. Chueh, P.W. Leu, J.C. Ho, T. Takahashi, L.A. Reichertz, S. Neale, K. Yu, M. Wu, J.W. Ager, and A. Javey. "Three-dimensional nanopillar-array photovoltaics on low-cost and flexible substrates," Nature Mat 8:648-653(2009).

Preuss, Paul. “Nanopillars Promise Cheap, Efficient, Flexible Solar Cells,” Berkeley Lab News Center (, July 9, 2009.


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High-Efficiency, Self-Concentrating Nanoscale Solar Cell, IB-2338

High Efficiency Tandem Silicon Solar Cells, IB-2357

Processing Iron Pyrite Nanocrystals for Use in Solar Cells, IB-2636

Non-sintered, Layered Nanocrystal Photovoltaic Cells, IB-2511

Hot Electron Photovoltaics Using Low Cost Materials and Simple Cell Design, IB-2195


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